OCT is an interferometric and spectrometric technique commonly used in the medical field for acquiring micrometer resolution images of biologic tissues. An OCT instrument focuses light on a tissue and reflected light is detected and analyzed. A combination of light reflected from the tissue and a reference light source give rise to an interference and spectrum pattern. Using this process, both, two and three-dimensional images of tissue is generated.
OCT may be used to image any biological tissue or tissue preparation. In the field of ophthalmology, OCT is commonly used for imaging the retina to evaluate a presence of glaucoma. For the detection of glaucoma, the retinal nerve fiber layer (RNFL)—which contains axons of ganglion cells, glial and other support cells—is isolated and measured. RNFL damage typically precedes visual field loss, and as such, detection of RNFL damage may yield early signs of glaucoma or other diseases of the nervous system. Nerve cell loss results in thinning of the RNFL and consequently, one or more areas of RNFL thinning may indicate a presence of glaucoma.
In the current state of the art, RNFL thickness is the only property that is observed by clinicians evaluating for glaucoma. However, testing RNFL thickness without observing or accounting for internal structures of the RNFL may lead to erroneous results and/or diminished sensitivity to glaucoma. If thickness is the only diagnostic metric, an error in the thickness detection algorithm will lead to an erroneous result. In addition, an area of localized thinning may be averaged out in a global RNFL thickness measurement and thereby missed. Furthermore, sectorial defects of the axonal bundles may be missed in the early stages of the diseases—before such defects give rise to detectable RNFL thinning.
The present invention utilizes a conventional OCT image, which contains other diagnostically important information that has heretofore not been recognized or utilized by practitioners and which may be used, either, independently or supplementary to conventional OCT for enhanced detection of glaucoma.